The invention relates to an information processing apparatus and, more particularly, to a data transfer system in various computers such as personal computer, workstation, server apparatus, office computer, minicomputer, main frame, super computer, and the like. Especially, the invention relates to an information processing apparatus by a crossbar switch in a multiprocessor apparatus.
In recent years, a multiprocessor construction has been widespread in an upper apparatus such as personal computer or workstation, a server apparatus, and the like. It is an important subject to improve the performance of a data transfer system for connecting among a plurality of CPUs (Central Processing Units), main storages, and I/O (Input/Output) devices.
As one of constructions of the data transfer systems, there is a construction by a crossbar switch connection. For example, this construction is disclosed in "The Advanced System Architecture", Sun World magazine, Vol. January, pp 29-32, 1996.
Generally, in the construction by the crossbar switch, even if any one of the modules which are connected to the crossbar switch fails, the other portions of the system can continue the operation. However, when at least a part of the crossbar switch itself fails, the whole system becomes down. Therefore, in order to improve the reliability of the whole system, it is necessary to duplicate the crossbar switch.
In many cases, the data transfer system has a construction by a bus connection. In this case, although the bus itself is hard to fail because it doesn't need any device such as an LSI (Large-Scale Integrated Circuit) or the like, there is a possibility such that the whole system is shut down when each module connected to the bus fails. Therefore, the bus is duplicated in order to improve the reliability of the system and such a method has been disclosed in, for example, JP-A-6-51910.